A novel type of multi-walled carbon nanotubes (MWNTS)/CO3O4 composite electrode for supercapacitors has been prepared through a facile and effective method, which combined the acid treatment of MWNTs and in situ decomposition of Co(NO3)(2) in n-hexanol solution at 140 degrees C. The samples are characterized by TEM, XRD and electrochemical testing, respectively. The MWNTs/Co3O4 composites show high capacitor property, and their best specific capacitance is up to 200.98 Fg(-1), which is significantly greater than that of pure MWNTs (90.1 Fg(-1)). With different MWNTs contents, they show Faradaic redox capacitive behavior to double-layer capacitive behavior, which may be due to the different microstructure of the composites. (c) 2007 Elsevier B.V. All rights reserved.